screen_ui: Drop the dependency on common.h.

Remove the use of fopen_path() in screen_ui.cpp, as this is the only
place that requires the dependency on common.h. The mounting work should
be done by the caller.

Also change the parameter in RecoveryUI::ShowFile() from const char* to
const std::string&.

Test: mmma -j bootable/recovery
Test: Build and boot into recovery image on angler. Choose 'View
      recovery logs'.
Change-Id: I8e63f14a8e2b12b856e5a92476e4226cd6ea39fb
diff --git a/screen_ui.h b/screen_ui.h
index 837d346..986959c 100644
--- a/screen_ui.h
+++ b/screen_ui.h
@@ -133,7 +133,7 @@
   // printing messages
   void Print(const char* fmt, ...) override __printflike(2, 3);
   void PrintOnScreenOnly(const char* fmt, ...) override __printflike(2, 3);
-  void ShowFile(const char* filename) override;
+  void ShowFile(const std::string& filename) override;
 
   // menu display
   int ShowMenu(const char* const* headers, const char* const* items, int initial_selection,